Jejunum histology. The intestines are thin and thick. Pathology of the duodenum

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1. 1. What is a cochlear implant and how is it different from hearing aids?

Hearing aids and assistive devices simply amplify sounds by making them louder, so even the most sophisticated hearing aids cannot help people with severe hearing loss.

In cochlear sensorineural hearing loss, the cochlear hair cells, which are responsible for converting the mechanical energy of sound into electrical impulses for the auditory nerve, die. But the nerve endings themselves function normally. The cochlear implant system is an electronic device that induces auditory sensations in the deaf by direct electrical stimulation of the nerve endings of the auditory nerve, thus simulating the work of dead cochlear hair cells.

Many years of research in the field of cochlear implantation have made it possible to work out and develop this technology. The first operations were carried out in the 1970s, and in the 80s the first multichannel devices appeared. At the same time, the first commercial operations were carried out.

Of course, the signals transmitted from the cochlear implant to the brain are different from the standard ones. In order to understand the speech addressed to him, a person will have to practice (rehabilitate) for several months according to a special program that will help to give obscure sounds a specific outline and help the brain get used to the new way of sound delivery. To date, such operations are the only way out for people with severe and profound hearing loss who are not helped by conventional hearing aids.

1. 2. Which is better for the deaf: a hearing aid or a cochlear implant?

It depends on many factors: the type of hearing loss, the degree of hearing impairment in the patient, his intelligence, degree of motivation, age, time and duration of hearing loss, as well as a number of other factors. The hearing aid helps the hard of hearing with hearing loss up to 80-90 dB. In turn, cochlear implants are more effective in cases of severe hearing loss and deafness in both ears, i.e. with a hearing loss of more than 90 dB.

1. 3. What companies produce CI?

Currently, several firms specialize in the creation of CIs. It:

• Cohlear (Australia)
• Med'El (Austria)
• Advanced Bionics (USA)
• MHM (Neurelec) (France)
• Nurotron (China)
• iEnjoy Sound (South Korea)

In Russia, implants from Cochlear, Med`El, Advanced Bionics and MXM (Neurelec) are certified and are being installed.

In Ukraine, implants from Cochlear, Med`El, Advanced Bionics are certified and placed.

1. 4. Which company is better to choose?

In principle, all firms are on an equal footing in the process of their technological development. Cochlear is considered the leader - also due to its prevalence in the world (about 70 percent of those implanted in the world). In second place is Med'El. However, in the US, for example, Advanced Bionics is the leader. According to the reviews of those who have been rehabilitated for a long time, the difference in the sound quality of implants from different companies is approximately the same. In any case, when choosing a manufacturer, you should proceed from your financial capabilities, the price of the system as a whole (as well as spare parts for it), and the presence of a tuner of this company in the area of ​​\u200b\u200bthe place of residence.

1. 5. What is the principle of operation of CI?

The cochlear implant system consists of an implant, an external speech processor, and external components such as a transmitter, cables, etc. The speech processor encodes the signal received from the microphone. The microphone converts acoustic signals into electrical signals.

Electrical signals are converted into a sequence of electrical pulses in accordance with a special coding strategy. The encoded signal is sent to the transmitter, which sends this sequence via radio signals through the skin to the implant.

The transmitter is worn under the hair behind the ear and is held in place with a magnet and earhook.

The implantable part consists of a ceramic or titanium body, a reference electrode (sometimes missing) and a chain of active electrodes. The implant contains electronics hermetically sealed in the housing. The impulses are fed to the electrode carrier for electrical stimulation of the auditory nerve.

The speech processor uses batteries that provide power to both external components and the electronics of the implanted part of the system through the radio frequency path. The implantable part does not contain batteries.

Functional Diagram of the Cochlear Implant System

1) Sound waves are received by the microphone.

2) The speech processor converts the acoustic signal into a rapid sequence of short electrical impulses in accordance with a special audio signal processing strategy.

3) The encoded signal is transmitted via cable to the transmitter.

4) The transmitter sends the signal and the necessary power through the RF path to the implant.

5) Electrical impulses stimulate various parts of the auditory nerve. The auditory nerve, performing its natural functions, transmits nerve impulses to the brain.

6) The brain receives nerve impulses and interprets them as sound, forming a sound image.

6. What is the cost of a CI operation?

The cost of CI depends on the manufacturer and model of CI. In general, you can focus on the range from 14 to 35 thousand euros for the device, operation and setup.

1. 7. Do they put CI in Russia or Ukraine? Where exactly can CI be placed in Russia or Ukraine?

Yes, in Russia CIs are engaged in operations. Since CI is an extremely expensive device, the vast majority of these operations are paid for by the state as part of the provision of highly specialized medical care.

Operations are carried out:

• Federal State Institution "Russian Scientific and Practical Center for Audiology and Hearing Prosthetics" (RSPCAiS)
• Federal State Institution "Scientific and Clinical Center of Otolaryngology"
• Moscow Scientific and Practical Center of Otorhinolaryngology
• Research Institute of Neurosurgery named after N.N. Burdenko (on a paid basis)

Moscow region

• Moscow Regional Research Clinical Institute. M.F.Vladimirsky (MONIKI)

St. Petersburg

• St. Petersburg Research Institute of Ear, Throat, Nose and Speech
• FBGUZ "Clinical Hospital No. 122 named. L.G. Sokolov FMBA of Russia "(MSCh 122)

There are also operations based on local hospitals by surgeons from Moscow and St. Petersburg, in particular, in Yekaterinburg, Ufa, Krasnodar, Voronezh and other cities.

In Ukraine, the situation is somewhat more complicated, there is a queue for operations, and mostly children are operated on.

• Kyiv Research Institute of Otorhinolaryngology. A.I. Kolomiichenko

1. 8. Is it possible to put CI for free?

Because CI is an extremely expensive device, the vast majority of these surgeries are paid for by the government through a tertiary care program.

However, in essence, the operation is not completely free, since funds are needed for:

• Preliminary examinations to determine indications for CT;
• hospital admission;
• Setting up the device in the future, after the first session of settings;

For non-residents additional funds are needed for:

• Tickets to the city (2 round-trip tickets - at least), if there is a disability, trips can be issued free of charge, since the state pays for the trip of a disabled person to the place of treatment;
• Living in the city for 1-3 months in total;

1. 9. How to get to the operation? What is needed for this? What is the procedure for referring a patient for examination for CT?

The direction of patients for cochlear implantation in federal medical institutions is carried out by the heads of the health authorities of the constituent entities of the Russian Federation, the Ministry of Health of the Russian Federation and its structural divisions. The procedure for referring citizens to cochlear implantation (a type of high-tech medical care - HMP) is established by order of the Ministry of Health and Social Development of the Russian Federation No. 786n dated December 29, 2008 (Appendix 7) federal budget appropriations account. (Note: The order is updated every year.)

The procedure for the patient or the child's parents is as follows:

• Contact the attending physician (audiologist) at the place of residence.
• The following is sent from the medical institution to the committee (department, administration, ministry) of health of the subject of the Federation: a referral from the head of the medical organization (or an authorized official) at the place of observation and (or) treatment of the patient; an extract from the patient's medical records containing information about the state of health and the examination and treatment carried out, recommendations on the need to refer to a medical institution for the provision of HTMC, the results of clinical diagnostic examinations carried out according to the profile of the disease; a copy of the identity document of a citizen of the Russian Federation with data on the place of his residence or stay; certificate of compulsory pension insurance of one of the parents or legal representative (for children). The procedure for issuing a quota for high-tech medical care (HMP). The commission of the subject of the Russian Federation decides on the presence (absence) of indications for the planned referral of a patient for the provision of HTMC to a federal medical institution. The commission is held with the involvement of the chief full-time or freelance specialist of the executive authority of the constituent entity of the Russian Federation in the field of healthcare according to the profile of the patient's disease.
• The protocol of the decision of the Commission of the subject of the Russian Federation is sent to the medical organization that sent the patient's documents, and to the federal medical institution.
• The medical institution determines the date of the patient's call.
• As a rule, all patients need an additional examination, after which the Commission of the federal medical institution makes a decision on the advisability of cochlear implantation.
• After the examination, the patient's data is entered into the waiting list (queue), according to which the patient is called for surgery.

A citizen of the Russian Federation has the right to appeal against decisions made during the procedure for referral to a medical institution for the provision of HTMC at any stage. A citizen can apply directly to the health authority of the constituent entity of the Russian Federation, the department of high-tech assistance of the Ministry of Health and Social Development.

Options for decisions of the Commission of the medical institution are given above, if necessary, for example, preliminary hearing aid, a decision can be made to conduct a re-examination after a certain period.

In addition, the patient can go directly to a federal cochlear implant facility for faster referral, or the patient can be self-supported by the center. In any case, the decision of the commission will be sent to the healthcare authority of the constituent entity of the Russian Federation, that is, the patient will be able to receive a referral for surgery in the future at the expense of the Federal budget.

If the patient does not want to wait or is not a citizen of the Russian Federation, the operation can be performed on a self-supporting basis.

MED-EL Implants

MED-EL implants

The implant consists of a small body, a chain of electrodes and a reference electrode.

Duodenum

Features of the structure of the duodenum ( duodenum) are determined mainly by the presence of duodenal glands in the submucosa (the so-called Brunner's glands). In this section of the small intestine, the ducts of two large glands open - the liver and pancreas. Chyme from the stomach enters the duodenum and undergoes further processing by enzymes of intestinal and pancreatic juices and bile acids. Here, active absorption processes begin.

Duodenal (Brunner's) glands. In phylogenesis, duodenal glands appear in mammals, which is due to the intensification of digestion processes due to an increase in the energy consumption of the body. In embryogenesis in mammals and humans, the duodenal glands are laid down and differentiate later than other glands - after the pancreas, liver, glands. Differences in the structure and function of the glands are associated with the nature of animal nutrition (herbivorous, carnivorous, omnivorous). In humans, the duodenal glands are laid on the 20-22nd week of embryogenesis. They are located in the submucosa along the entire length of the duodenum. Almost half of the glandular field (~43%) is occupied by a zone of compact arrangement of lobules (compact-diffuse zone), followed by a columnar zone (in the folds of the mucous membrane) and in the caudal part - a zone of single lobules.

Po are alveolar-tubular, branched glands. Their excretory ducts open into crypts, or at the base of the villi directly into the intestinal cavity. Glandulocytes of the terminal sections are typical mucous (mucosal) cells with characteristic secretion granules. The cambial elements are located at the mouth of the ducts; therefore, the renewal of the cells of the glands proceeds from the ducts towards the terminal sections. In the duodenal glands there are endocrinocytes of various types - EC, G, S, D.

The secret of glandulocytes is rich in neutral glycoproteins with terminal disaccharides present in them, in which galactose is associated with galactosamine or glycosamine residues. In glandulocytes, synthesis, accumulation of granules and secretion are constantly noted simultaneously.

In the resting phase (out of food intake) in the glandulocytes of the duodenal glands, slightly pronounced processes of synthesis and exocytosis of secretory granules take place. When eating, there is an increase in secretion by exocytosis of granules, apocrine, and even secretion by diffusion. The asynchrony of the work of individual glandulocytes and various terminal sections ensures the continuity of the functioning of the duodenal glands.

The secret of the duodenal glands, connecting with the parietal layer of mucus, gives it greater viscosity and resistance to destruction. Mixing with duodenal intestinal juice, the secret of these glands contributes to the formation of gel particles - flocculus, formed when the pH in the duodenum decreases due to the intake of acidified chyme from the stomach. These floccules significantly increase the adsorption properties of intestinal juice for enzymes, which increases the activity of the latter. For example, the adsorption and activity of the enzyme trypsin in the structures of the dense phase of the intestinal juice (after adding the secret of the duodenal glands to it) increase by more than 2 times.

Thus, the secret of the duodenal glands has the maximum ability to flocculation (at certain pH values), stimulates the structuring of the duodenal juice and increases its sorption properties. The absence of secretion of duodenal glands in the composition of chyme and parietal mucus changes their physicochemical properties, resulting in a decrease in the sorption capacity for endo- and exohydrolases and their activity.

Accumulations of lymphoid tissue in the small intestine

Lymphoid tissue (GALT, which is part of) is widely distributed in the small intestine in the form of lymph nodes and diffuse accumulations of lymphocytes and performs a protective function.

Solitary (so-called solitary) lymphoid nodules ( noduli lymphatici solitarii) are found throughout the small intestine in the mucosa. Their diameter is about 0.5-3 mm. Larger nodules lying in the distal parts of the small intestine penetrate into the muscular plate of its mucous membrane and are partially located in the submucosa. The number of single lymphoid nodules in the wall of the small intestine of children from 3 to 13 years old is about 15,000. As the body ages, their number decreases.

Clustered lymphoid nodules ( noduli lymphatic aggregati), or Peyer's patches, as a rule, are located in the ileum, but sometimes occur in the jejunum and duodenum. The number of nodules varies depending on age: in the small intestine in children there are about 100, in adults - about 30-40, and in old age their number decreases significantly.

The length of one grouped lymphoid nodule can be from 2 to 12 cm, and the width is about 1 cm. The largest of them penetrate the submucosa. Villi in the mucous membrane at the locations of grouped lymphoid nodules are usually absent.

For the epithelial lining located above the nodules; It is typical, as already mentioned, that M-cells(cells with microfolds) through which antigens that stimulate lymphocytes are transported. Plasma cells formed in the follicles secrete immunoglobulins (IgA, IgG, IgM), the main of which is IgA. For one plasma cell secreting IgG, there are 20-30 plasma cells producing IgA and 5 producing IgM. IgA, unlike other immunoglobulins, are more active, since they are not destroyed by intestinal proteolytic enzymes. Resistance to intestinal proteases is due to the combination of IgA with a secretory component formed by epithelial cells. In epithelial cells, a glycoprotein is synthesized, which is included in their basal plasma membrane (transmembrane glycoprotein) and serves as an Fc receptor for IgA. When IgA is combined with the Fc receptor, a complex is formed, which enters the epitheliocyte by endocytosis and, as part of a transcytic vesicle, is transferred to the apical part of the cell and released into the intestinal lumen by exocytosis through the apical plasmolemma. When this complex is released into the intestinal lumen, only a part of the glycoprotein is cleaved from it, which is directly associated with IgA and is called the secretory component. The rest of it (the "tail" of the molecule) remains in the composition of the plasmalemma. In the intestinal lumen, IgA performs a protective function, neutralizing antigens, toxins, and microorganisms.

Vascularization. Arteries, entering the wall of the small intestine, form three plexuses: intermuscular - between the inner and outer layers of the muscular membrane; broadly looped - in the submucosa and narrowly looped - in the mucous membrane. Arterioles emerge from the latter, forming blood capillaries around the intestinal crypts, and 1-2 arterioles entering each villus and disintegrating there into capillary networks. From the blood capillaries of the villus, blood is collected in a venule that runs along its axis. The veins of the small intestine form two plexuses - a plexus in the mucosa and a plexus in the submucosa. There are numerous arteriovenular anastomoses of the type of trailing arteries that regulate blood flow to the intestinal villi. During the act of digestion, the anastomoses between the arteries and veins are closed, and the entire mass of blood rushes into the mucous membrane, to its villi. During the fasting period, the anastomoses are open and the bulk of the blood passes through the mucous membrane. The obstructing veins regulate the volume of venous outflow from the small intestine. In the event of a sharp overflow, these veins can deposit significant amounts of blood.

Lymphatic vessels small intestine are represented by a very widely branched network. In each intestinal villus there is a centrally located, blindly ending at its top, a lymphatic capillary. Its lumen is wider than in the blood capillaries. From the lymphatic capillaries of the villi, the lymph flows into the lymphatic plexus of the mucous membrane, and from it into the corresponding plexus of the submucosa, formed by larger lymphatic vessels. A dense network of capillaries also flows into this plexus, braiding single and group lymphatic nodules. From the submucosal plexus depart the lymphatic vessels located between the layers of the muscular membrane.

innervation. Afferent innervation is carried out by the musculo-intestinal sensory plexus ( plexus myentericus sensibilis), formed by sensory nerve fibers of the spinal ganglia and their receptor endings. Branched and bushy nerve endings are often found in the submucosa and lamina propria. Their terminal branches reach vessels, duodenal glands, epithelium of intestinal crypts and villi. Abundant branching of sensory fibers is observed in the ileum and ileocecal region, where bushy forms of receptors predominate. Separate receptors are present in the nerve ganglia themselves.

Efferent innervation is carried out by sympathetic and parasympathetic nerves. In the thickness of the intestinal wall, the parasympathetic musculo-intestinal and submucosal nerve plexuses are well developed. musculoskeletal plexus ( plexus myentericus) is most developed in the duodenum, where numerous, densely located large ganglia are observed. The number and size of ganglia in the small intestine decrease in the caudal direction. In the ganglia, Type I and Type II Dogel cells are distinguished, with much more Type I cells. The small intestine, in comparison with other parts of the digestive tube, is characterized by the presence of a large number of type II cells. There are especially many of them in the duodenum, in the initial section of the ileum and in the ileocecal region.

Features of the structure and function of the vessels of the microvasculature of the intestinal villi

The blood and lymphatic vessels of the villi are actively involved in the absorption and transport of substances from food.

Blood vessels. The villus usually includes one precapillary arteriole located in the center or eccentrically. At the top of the villus, it divides into two distributive main capillaries, which descend along the two edges of the (marginally) leaf-shaped villus, located subepithelially. From the main (marginal) capillaries, fountain-like capillary networks (of 3-5 capillaries) are formed, which are located subepithelially along two flat walls (cranial and caudal) of the villi. These are hemocapillaries visceral type with fenestrated endotheliocytes, in which the nucleated part faces the stroma of the villus, and the fenestrated part with interendothelial contacts faces the epithelium. From the capillaries of the middle and lower parts of the villus, as a rule, one postcapillary venule is formed, from which blood enters the veins of the next stage.

The marginal capillaries along the edges of the villus constitute the shunting block, and the capillaries on its cranial and caudal surfaces form the absorption block. Their condition depends on the cycle of digestion (hunger or food intake). In a state of functional rest (starvation), the microvessels of the bypass block work as semi-shunts: blood flows along the central arteriole, from it along the marginal and further along the fountain-like capillaries of the cranial and caudal surfaces, and then into the venule. The capillaries of the subepithelial network of the cranial and caudal walls have a limited function.

With a functional load (food intake), marginal capillaries turn into resorbing vessels and all capillaries of the subepithelial network are included in the bloodstream.

Thus, with an increase in the absorption of food, all capillaries of the subepithelial networks on the cranial and caudal walls of the villus begin to function actively; additionally, the microvessels of the bypass unit are included in the absorption processes.

Lymph capillaries located in the upper and middle parts of the villi, at a constant distance from its ribs. There are tight and adhesive contacts between endotheliocytes, there is no basement membrane in the lymphocapillaries. In the contact zone, protein molecules of average relative molecular weight and lipids (in the form of chylomicrons) are transferred. When eating, open intercellular gaps appear due to the contraction of endotheliocytes.

In the extravascular transport of fluid, the intercellular substance of the connective tissue of the villi takes part. In the interstitial part of the villus, two zones can be distinguished - central and subepithelial.

In the subepithelial zone, there is an accumulation of proteins coming from hemocapillaries. Large concentrations of proteins in this zone are the most important factor that ensures the absorption of fluid from the intestinal plane (the so-called "oncotic pump"). The volume of the interstitial space in the central zone varies depending on the intake of fluid, proteins, lipids and can increase by more than 2 times, while in the subepithelial part it changes slightly. An increase in the protein concentration towards the basal part of the villus causes the masses of fluid to move from its apical parts to the base.

Thus, there are two vectors of interstitial fluid transport: 1 - radial - from the periphery of the villus to its center, 2 - axial - from the top of the villus to the base.

Filtration of fluid from hemocapillaries into the interstitial space of the villi occurs in a state of functional rest (starvation) and is due to an increase in hydrostatic and colloid osmotic pressure in the capillary due to relaxation of the precapillary sphincters. The flow of fluid from the plasma is balanced by the base level of lymphatic drainage, so the volume of the interstitial space of the villus remains constant.

With active absorption of substances from the intestinal lumen, a twofold increase in lymph flow occurs (part of the interstitial fluid is resorbed into hemocapillaries). In the flowing lymph, the amount of proteins that are intensively entering the interstitium increases. The protein content is higher in the subepithelial layer, which is associated with the presence of a dense network of capillaries here and the peculiarity of the structure of endotheliocytes (fenestra and intercellular contacts) in this zone. Special structures, short transendothelial channels and “leaky” intercellular contacts (convective pathways) play an important role in the transfer of proteins.

Strengthening of digestion processes leads to increased transport of proteins in most of the hemocapillaries and in the microvessels of the villus base, which is accompanied by intensive absorption of fluid from the intestinal cavity, primarily into the apical parts of the villus. The combined effect of fluid filtration from the capillaries and its entry from the intestinal cavity leads to hydration of the interstitial space and an increase in hydrostatic pressure; at the same time, the volume of the intercellular matrix increases by more than 2 times. Hydrostatic pressure in the upper and middle sections of the villi stimulates the process of resorption in the lymphocapillaries.

Histophysiology of the processes of digestion and absorption in the small intestine

Digestion in the small intestine includes two main processes: 1) further enzymatic processing of substances contained in chyme to final products and preparing them for absorption; 2) suction.

Digestion processes occur in different areas of the intestine, and therefore distinguish extracellular and intracellular digestion. Intracellular digestion is carried out already in the cytoplasm of enterocytes. Extracellular digestion is distinguished: cavitary (in the intestinal cavity), parietal (near the intestinal wall), membrane (on the apical parts of the plasmolemma of enterocytes and their glycocalyx).

Extracellular digestion in the intestinal cavity is carried out due to three components - enzymes of the digestive glands (salivary, pancreas), enzymes of the intestinal flora and enzymes of the food products themselves. Parietal digestion occurs in the mucous deposits of the small intestine, which adsorb various enzymes of cavity digestion, as well as enzymes secreted by enterocytes. Membrane digestion occurs at the border of the extracellular and intracellular environment. On the plasmolemma and glycocalyx of enterocytes, digestion is carried out by two groups of enzymes. The first group of enzymes is formed in the pancreas (α-amylase, lipase, trypsin, chymotrypsin, carboxypeptidase). They are adsorbed by the glycocalyx and microvilli, while the main amount of amylase and trypsin is adsorbed on the apical part of the microvilli, and chymotrypsin - on the lateral zones. The second group - enzymes of intestinal origin, they are associated with the plasma membrane of enterocytes.

Glycocalyx, in addition to the adsorption of enzymes involved in digestion, plays the role of a filter that selectively passes only those substances for which there are adequate enzymes. In addition, glycocalyx performs a protective function, providing isolation of enterocytes from bacteria and toxic substances formed by them. The glycocalyx contains receptors for hormones, antigens, and toxins.

intracellular digestion occurs inside columnar epitheliocytes, is provided by their enzymes, mainly located in lysosomes. Incompletely cleaved low molecular weight substances enter the epitheliocyte by endocytosis or transmembrane transfer. Endocytic vacuoles fuse with lysosomes and their contents are hydrolyzed by the appropriate hydrolases. This type of digestion is phylogenetically older. In vertebrates, intracellular digestion by endocytosis is observed only in the first days after birth. In this way, maternal antibodies found in colostrum and milk can be transmitted to newborns and provide their immunological protection.

The monomers formed during the breakdown of proteins, carbohydrates and fats - amino acids, monosaccharides, monoglycerides and fatty acids - are then absorbed into the blood and lymph through epitheliocytes.

Suction- this is the passage of the products of the final breakdown of food (monomers) through the epithelium, basement membrane, vascular wall and their entry into the blood and lymph. The histophysiology of absorption of the breakdown products of proteins, carbohydrates and fats has some peculiarities.

Absorption of fats- the most studied process. In humans, most lipids are absorbed in the duodenum and upper jejunum. The main role in the breakdown of lipids and their processing is played by lipases(pancreas and intestines) and hepatic bile.

Happens in the intestine fat emulsification with the help of bile acids coming with bile, while droplets are formed with a size of not more than 0.5 microns. Bile acids are also activators of pancreatic lipase, which breaks down emulsified triglycerides and diglycerides into monoglycerides. Intestinal lipase breaks down monoglycerides into fatty acids and glycerol. Cleavage occurs with the help of enzymes of the plasmolemma and glycocalyx of the enterocyte. Fatty acids with a short carbon chain and glycerol are highly soluble in water and are freely absorbed, entering through the portal vein to the liver. Fatty acids with a long carbon chain and monoglycerides are absorbed with the participation of bile salts, with which they form in the glycocalyx zone micelles with a diameter of 4-6 nm. Micelles are 150 times smaller than emulsified drops and consist of a hydrophobic core (fatty acids and glyceroids) and a hydrophilic shell (bile acids, phospholipids). As part of micelles, fatty acids and monoglycerides are transferred to the absorbent surface of the intestinal epithelium. There are two mechanisms for the entry of lipids into epitheliocytes: 1) by diffusion and pinocytosis of micelles, then their intracellular decay occurs with the release of the lipid component and bile acids, bile acids enter the blood, and then to the liver; 2) only micelle lipids enter epitheliocytes, while bile acids remain in the intestinal lumen and are further absorbed into the blood. There is a constant recirculation of bile acids between the liver and intestines (enterohepatic circulation). It involves the bulk of bile acids - 85-90% of their total amount.

Micelles penetrate through the plasma membrane by diffusion or micropinocytosis and enter the Golgi apparatus, where fat is resynthesised. Proteins are attached to fats, and lipoprotein complexes are formed - chylomicrons. With the introduction of small amounts of fat in the Golgi apparatus with food, a small amount of lipids accumulate within 1 hour, with the introduction of large amounts of fat, lipids accumulate within 2 hours in the Golgi apparatus and in small vesicles of the apical part of enterocytes. The fusion of these small vesicles with elements of the Golgi apparatus leads to the formation of large lipid droplets.

In epithelial cells, there is a resynthesis of fats specific for this type of animal; they enter the cytoplasm of most cells and tissues. The resynthesis of fats from fatty acids and monoglycerides occurs with the help of enzymes (monoglyceride lipase, glycerol kinase), while triglycerides (especially glycerophospholipids) are formed. Glycerophospholipids are resynthesized in epitheliocytes from fatty acids, glycerol, phosphoric acid, and nitrogenous bases.

Cholesterol comes with food in free form or in the form of its esters. The enzyme of pancreatic and intestinal juices - cholesterolesterase - breaks down cholesterol esters into cholesterol and fatty acids, which are absorbed in the presence of bile acids.

Resynthesized triglycerides, phospholipids, cholesterol combine with proteins and form chylomicrons - small particles with a diameter of 100 to 5000 nm (0.2-1 microns). They contain more than 80% triglycerides, cholesterol (8%), phospholipids (7%) and protein (2%). By exocytosis, they are released from epitheliocytes on their lateral surface, enter the interepithelial spaces, connective tissue matrix and lymphocapillaries. From the lymphocapillaries, chylomicrons enter the lymph of the thoracic duct and then into the bloodstream. After taking fats with food, after 1-2 hours, the concentration of triglycerides in the blood increases and chylomicrons appear, after 4-6 hours their content becomes maximum, and after 10-12 hours - normal, and they completely disappear. Most of the chylomicrons enter the lymphatic capillaries and a little into the hemocapillaries. Lipids with long carbon chains enter mainly into the lymphatic capillaries. Fatty acids with fewer carbon atoms enter the hemocapillaries.

Absorption of carbohydrates. The breakdown of glycogen and starch molecules to maltose is carried out by pancreatic a-amylase and glucosides. Further, maltose is hydrolyzed by the enzyme maltase into 2 molecules of glucose, and sucrose by the enzyme sucrase into molecules of glucose and fructose. Lactose in milk is broken down into glucose and galactose by the enzyme lactase. The resulting monosaccharides (glucose, fructose and galactose) are absorbed by enterocytes and enter the bloodstream.

Polysaccharides and disaccharides (maltose, sucrose, lactose), which have not undergone cleavage in the intestinal cavity, are hydrolyzed on the surface of enterocytes during parietal and membrane digestion. For the absorption of simple sugars, Na + ions are needed, which form a complex with carbohydrates and enter the cell, where the complex breaks down and Na + is transported back. The process is powered by ATP. More than 90% of the absorbed monosaccharides enter the hemocapillaries and then to the liver, the rest - to the lymphocapillaries and then to the venous system.

Protein absorption in newborns occurs with the help of pinocytosis. Pinocytic vesicles form between the bases of microvilli, are transported to the lateral walls (plasmolemms) of enterocytes, and are secreted by exocytosis into the interepithelial space and further into the vessels. In this way, γ-globulins are absorbed from mother's milk, which provide immune protection for the newborn.

In adults, protein breakdown begins in the stomach and then continues in the small intestine until amino acids are formed, which are absorbed. Intestinal juice contains pancreatic enzymes - proteinases (trypsin, chymotrypsin, collagenase) and peptidases (carboxypeptidase, elastase), intestinal enzymes - enterokinase (a glycoprotein synthesized in the duodenum) and a number of peptidases (aminopeptidase, leucine aminopeptidase, tripeptidases, dipeptidases, etc. .).

Duodenum(lat. duodenum) - the initial section of the small intestine, following immediately after the pylorus. The continuation of the duodenum is the jejunum.

Anatomy of the duodenum

The duodenum got its name from the fact that its length is about twelve finger widths. The duodenum does not have a mesentery and is located retroperitoneally.

The figure shows: duodenum (in Fig. English Duodenum), pancreas, as well as bile and pancreatic ducts, through which bile and pancreatic secretion enter the duodenum: the main pancreatic duct (Pancreatic dust), additional (Santorini) pancreatic duct (Accessory pancreatic duct), common bile duct (Common bile-duct), large duodenal (vater) nipple (Orifice of common bile-duct and pancreatic duct).

Functions of the duodenum

The duodenum performs secretory, motor and evacuation functions. Duodenal juice is produced by goblet cells and duodenal glands. Pancreatic juice and bile enter the duodenum, providing further digestion of nutrients that has begun in the stomach.

Sphincters of the duodenum and the papilla of Vater

On the inner surface of the descending part of the duodenum, about 7 cm from the pylorus, there is a Vater nipple, in which the common bile duct and, in most cases, the pancreatic duct combined with it, open into the intestine through the sphincter of Oddi. In about 20% of cases, the pancreatic duct opens separately. Above the nipple of Vater, 8–40 mm may be santorini nipple, through which the additional pancreatic duct opens.

Endocrine cells of the duodenum

The Lieberkühn glands of the duodenum contain the largest set of endocrine cells among other organs of the gastrointestinal tract: I-cells that produce the hormones cholecystokinin, S-cells - secretin, K-cells - glucose-dependent insulinotropic polypeptide, M-cells - motilin, D-cell and - somatostatin, G-cells - gastrin and others.

Short chain fatty acids in the duodenum

In human duodenal contents, the main share of short-chain fatty acids (SCFA) is acetic, propionic and butyric. Their number in 1 g of duodenal contents is normal (Loginov V.A.):

• acetic acid - 0.739±0.006 mg
• propionic acid - 0.149±0.003 mg
• butyric acid - 0.112±0.002 mg

duodenum in children

The duodenum of a newborn is located at the level of the 1st lumbar vertebra and has a rounded shape. By the age of 12, it descends to the III-IV lumbar vertebra. The length of the duodenum up to 4 years is 7–13 cm (in adults up to 24–30 cm). In young children, it is very mobile, but by the age of 7, adipose tissue appears around it, which fixes the intestine and reduces its mobility (Bokonbaeva S.D. and others).

Some diseases and conditions of the duodenum

Some diseases of the duodenum (DUD) and syndromes:

It contains the small and large intestines. The small intestine includes the duodenum, jejunum, and ileum.

Small intestine

Saves mechanical function - provides the promotion of chyme, increases dramatically hydrolysis food products, which is carried out with the help of intestinal juice. It is saturated with hydrolytic enzymes, which are able to break down almost all known biological substances. All enzymes operate at pH=8.5-9.

Proteins - trypsin, dipeptidase, enterokinase, nuclease, chemotrypsin.

Carbohydrates - maltase, amylase, sucrase.

Lipids are lipase.

The pancreas, duodenal glands and intestinal glands are involved in the formation of intestinal juice - a set of cellular glandular elements that are contained in the intestine.

Available suction function, and water is absorbed little, mostly nutrients. excretory function is characteristic of the intestine to a small extent. The intestine also provides local immune protection.

The wall contains 4 shells throughout.

The inner surface of the small intestine is extremely uneven - there are circular folds that are formed by the mucosa and submucosa, they divide the small intestine into segments, increasing the working surface of the intestine and creating conditions for digestion. The chyme passes through 7 meters of the intestine in a few hours, that is, the folds provide discrete passage of the chyme. There are about 4 million intestinal villi. These are finger-like thin outgrowths of the mucous membrane in the lumen of the small intestine, the maximum frequency of the location of the villi is in the duodenum. They are wide and low. Then they meet less in the course of the small intestine, but become thin and long. There are up to 150 million crypts - intestinal glands. A crypt is a deepening of the mucosal epithelium into the underlying connective tissue. Around each villus there are several crypts.

The mucous membrane is expelled by a single-layer prismatic border epithelium. The epithelium lining the intestinal villi contains bordered enterocytes. These are tall cylindrical cells with moderately developed organelles. At the top contains up to 3 thousand microvilli. Between the microvilli and above them there is a network of thin fibrils - the glycocalyx. Hydrolytic and transport enzymes are located on the fibrils, which provide parietal digestion and transport of substances from the border zone into the cells. Microvilli increase the absorption surface by 10-40 times (maximum - in the duodenum) and prevent the penetration of organisms, especially Escherichia coli. Between the limbic enterocytes in a much smaller number lie goblet cells. They produce and secrete a mucous secretion onto the surface of the intestine. Between these cells are endocrine cells diffuse endocrine system. Therefore, the endocrine function is characteristic of the small intestine. The number of endocrine cells is maximum in the duodenum and decreases in the underlying sections.

In the upper half of the epithelium of the crypts there are cylindrical cells with a weakly pronounced border. The lower half of the crypts contains a large number of goblet cells. In the bottom of the crypts there is a large number of endocrine cells and the so-called acidophilic-granular cells. They contain protein secretory granules and produce and secrete enzymes that break down proteins, mainly dipeptidases. In the epithelium of the lower part of the crypts there are poorly differentiated stem cells. They proliferate and differentiate - partly into acidophilic granular cells, endocrine cells, goblet cells. A large number of young cells move along the basal membrane to the upper part of the crypts and differentiate into kinky enterocytes, then move along the surface of the villi, reaching maximum differentiation in the middle third of the intestinal villi. Then they move to the top of the intestinal villi. Here they die and are exfoliated into the intestinal lumen. Complete renewal of the epithelium of the intestinal villi occurs in 3-6 days. The stroma of the intestinal villi is made up of loose connective tissue - part of the mucosal lamina propria, which contains a dense capillary network - closer to the basement membrane, in the center there is a lymphatic capillary and in the center there is a bundle of smooth muscle cells.

Along the course of the small intestine, the number of mucous cells in the epithelium increases, the number of border enterocytes, endocrine cells and cells with acidophilic granularity decreases.

The lamina propria of the loose connective tissue forms the stroma of the intestinal villi and is located in narrow layers between the intestinal crypts. Contains blood and lymphatic capillaries, thin nerve fibers, up to 10 thousand lymphatic nodules, which form clusters in the ileum. In the epithelium opposite the lymph nodes are the so-called M cells- microfolded cells. They are lower than the bordered enterocytes, they have short microvilli, they are wider and form depressions (folds) in which immunocompetent cells, usually lymphocytes, are located. M-cells are arranged in microfields. These cells take up antigens from the intestinal lumen and pass the antigens to the lymph nodes.

The muscular plate contains an inner circular layer and an outer one - a longitudinal one. From it depart bundles of smooth muscle cells in the intestinal villi. It promotes the contraction of the intestinal villi. Contraction of the mucosa and secretion from the intestinal villi.

The submucosa is formed by loose, unformed connective tissue. Contains large vascular and nerve plexuses. The widest is in the duodenum and contains the duodenal glands here. These are complex branched tubular glands that open into intestinal crypts. Their secretory section contains mucous cells, goblet cells, acidophilic granular cells, chief and parietal cells. These glands are involved in the formation of intestinal juice. Everywhere, except for the duodenum, the submucosa is thin.

The muscular layer is built from smooth muscle tissue. The inner circular and outer longitudinal layers are well developed. Between them lies the intermuscular nerve plexus. The contraction of the muscular membrane ensures the movement of chyme through the small intestine.

The outer shell is represented by a sheet of peritoneum, which contains a lot of nerve receptors and nerve plexuses. From the surface, the serous membrane is moistened with mucous secretion and is constantly in motion.

SMALL INTESTINE

Anatomically, the small intestine is divided into the duodenum, jejunum, and ileum. In the small intestine, proteins, fats, carbohydrates undergo chemical processing.

Development. The duodenum is formed from the final section of the anterior intestine of the initial section of the middle, a loop is formed from these rudiments. The jejunum and ileum are formed from the remainder of the midgut. 5-10 weeks of development: a loop of growing intestine is "pushed" out of the abdominal cavity into the umbilical cord, and the mesentery grows up to the loop. Further, the loop of the intestinal tube "returns" to the abdominal cavity, it rotates and further grows. The epithelium of the villi, crypts, duodenal glands are formed from the endoderm of the primary intestine. Initially, the epithelium is single-row cubic, 7-8 weeks - single-layer prismatic.

8-10 weeks - the formation of villi and crypts. 20-24 weeks - the appearance of circular folds.

6-12 weeks - differentiation of epitheliocytes, columnar epitheliocytes appear. The beginning of the fetal period (from 12 weeks) is the formation of a glycocalyx on the surface of epitheliocytes.

Week 5 - differentiation of goblet exocrinocytes, week 6 - endocrinocytes.

7-8 weeks - the formation of the own plate of the mucous membrane and the submucosa from the mesenchyme, the appearance of the inner circular layer of the muscular membrane. 8-9 weeks - the appearance of the outer longitudinal layer of the muscular membrane. 24-28 weeks there is a muscular plate of the mucous membrane.

The serous membrane is laid at the 5th week of embryogenesis from the mesenchyme.

The structure of the small intestine

In the small intestine, the mucous membrane, submucosa, muscular and serous membranes are distinguished.

1. Structural and functional unit of the mucous membrane are intestinal villi- protrusions of the mucous membrane, freely protruding into the intestinal lumen and crypts(glands) - deepening of the epithelium in the form of numerous tubules located in the lamina propria of the mucous membrane.

mucous membrane consists of 3 layers - 1) a single-layer prismatic border epithelium, 2) its own layer of the mucous membrane and 3) the muscular layer of the mucous membrane.

1) Several populations of cells are distinguished in the epithelium (5): columnar epitheliocytes, goblet exocrinocytes, exocrinocytes with acidophilic granules (Paneth cells), endocrinocytes, M cells. The source of their development is stem cells located at the bottom of the crypts, from which progenitor cells are formed. The latter, mitotically dividing, then differentiate into a specific type of epithelium. Progenitor cells, being in the crypts, move in the process of differentiation to the top of the villus. Those. the epithelium of crypts and villi represents a single system with cells at various stages of differentiation.

Physiological regeneration is provided by mitotic division of progenitor cells. Reparative regeneration - a defect in the epithelium is also eliminated by cell reproduction, or - in the case of gross damage to the mucosa - is replaced by a connective tissue scar.

In the epithelial layer in the intercellular space there are lymphocytes that carry out immune protection.

The crypt-villus system plays an important role in the digestion and absorption of food.

intestinal villus – from the surface it is lined with a single-layer prismatic epithelium with three main types of cells (4 types): columnar, M-cells, goblet, endocrine (their description in the Crypt section).

Columnar (border) epithelial cells of the villi- on the apical surface, a striated border formed by microvilli, due to which the suction surface increases. There are thin filaments in the microvilli, and on the surface there is a glycocalyx, represented by lipoproteins and glycoproteins. The plasmalemma and glycocalyx contain a high content of enzymes involved in the breakdown and transport of absorbable substances (phosphatases, aminopeptidases, etc.). The processes of splitting and absorption occur most intensively in the region of the striated border, which is called parietal and membrane digestion. The terminal network present in the apical part of the cell contains actin and myosin filaments. There are also connecting complexes of dense insulating contacts and adhesive belts that connect neighboring cells and close the communication between the intestinal lumen and intercellular spaces. Under the terminal network there are tubules and cisterns of the smooth endoplasmic reticulum (processes of fat absorption), mitochondria (energy supply of absorption and transport of metabolites).

In the basal part of the epitheliocyte there is a nucleus, a synthetic apparatus (ribosomes, granular ER). Lysosomes and secretory vesicles formed in the area of ​​the Golgi apparatus move to the apical part and are located under the terminal network.

Secretory function of enterocytes: production of metabolites and enzymes necessary for parietal and membrane digestion. The synthesis of products occurs in the granular ER, the formation of secretory granules occurs in the Golgi apparatus.

M cells- cells with microfolds, a type of columnar (marginal) enterocytes. They are located on the surface of Peyer's patches and single lymphatic follicles. On the apical surface of microfolds, with the help of which macromolecules are captured from the intestinal lumen, endocytic vesicles are formed, which are transported to the basal plasmolemma, and then to the intercellular space.

goblet exocrinocytes located singly among columnar cells. By the end of the small intestine, their number increases. Changes in cells proceed cyclically. The secret accumulation phase - the nuclei are pressed to the base, near the nucleus, the Golgi apparatus and mitochondria. Drops of mucus in the cytoplasm above the nucleus. The formation of the secret occurs in the Golgi apparatus. At the stage of accumulation of mucus in the cell, altered mitochondria (large, light with short cristae). After secretion, the goblet cell is narrow; there are no secretion granules in the cytoplasm. The secreted mucus moisturizes the surface of the mucosa, facilitating the movement of food particles.

2) Under the epithelium of the villus there is a basement membrane, behind which is a loose fibrous connective tissue of the lamina propria. It contains blood and lymph vessels. Blood capillaries are located under the epithelium. They are of the visceral type. Arteriole, venule and lymphatic capillary are located in the center of the villus. In the stroma of the villus there are separate smooth muscle cells, the bundles of which are entwined with a network of reticular fibers that connect them with the stroma of the villus and the basement membrane. The contraction of smooth myocytes provides a "pumping" effect and enhances the absorption of the contents of the intercellular substance into the lumen of the capillaries.

intestinal crypt . Unlike villi, it contains, in addition to columnar epitheliocytes, M-cells, goblet cells, stem cells, progenitor cells, differentiating cells at different stages of development, endocrinocytes and Paneth cells.

Paneth cells located singly or in groups at the bottom of the crypts. They secrete a bactericidal substance - lysozyme, an antibiotic of a polypeptide nature - defensin. In the apical part of the cells, strongly refracting light, sharply acidophilic granules when stained. They contain a protein-polysaccharide complex, enzymes, lysozyme. In the basal part, the cytoplasm is basophilic. The cells revealed a large amount of zinc, enzymes - dehydrogenases, dipeptidases, acid phosphatase.

Endocrinocytes. There are more of them than in the villi. EC-cells secrete serotonin, motilin, substance P. A-cells - enteroglucagon, S-cells - secretin, I-cells - cholecystokinin and pancreozymin (stimulate the functions of the pancreas and liver).

lamina propria of the mucous membrane contains a large number of reticular fibers forming a network. They are closely related to process cells of fibroblastic origin. There are lymphocytes, eosinophils, plasma cells.

3) Muscular plate of the mucosa consists of an inner circular (individual cells go into the lamina propria of the mucous membrane), and an outer longitudinal layer.

2. Submucosa It is formed by loose fibrous irregular connective tissue and contains lobules of adipose tissue. It contains the vascular collectors and the submucosal nerve plexus. .

Accumulation of lymphoid tissue in the small intestine in the form of lymphatic nodules and diffuse accumulations (Peyer's patches). Solitary throughout, and diffuse - more often in the ileum. Provide immune protection.

3. Muscular membrane. Inner circular and outer longitudinal layers of smooth muscle tissue. Between them is a layer of loose fibrous connective tissue, where the vessels and nodes of the nervous musculo-intestinal plexus. Carries out mixing and pushing the chyme along the intestine.

4. Serous membrane. Covers the intestine from all sides, with the exception of the duodenum, covered with peritoneum only in front. It consists of a connective tissue plate (PCT) and a single-layer, squamous epithelium (mesothelium).

Duodenum

The feature of the structure is the presence duodenal glands in the submucosa, these are alveolar-tubular, branched glands. Their ducts open into crypts or at the base of the villi directly into the intestinal cavity. Glandulocytes of the terminal sections are typical mucous cells. The secret is rich in neutral glycoproteins. In glandulocytes, synthesis, accumulation of granules and secretion are simultaneously noted. Secret function: digestive - participation in the spatial and structural organization of hydrolysis and absorption processes and protective - protects the intestinal wall from mechanical and chemical damage. The absence of a secret in the chyme and parietal mucus changes their physicochemical properties, while the sorption capacity for endo- and exohydrolases and their activity decrease. The ducts of the liver and pancreas open into the duodenum.

Vascularization small intestine . Arteries form three plexuses: intermuscular (between the inner and outer layers of the muscular membrane), wide-looped - in the submucosa, narrow-looped - in the mucous membrane. Veins form two plexuses: in the mucosa and submucosa. Lymphatic vessels - in the intestinal villus, a centrally located, blindly ending capillary. From it, the lymph flows into the lymphatic plexus of the mucous membrane, then into the submucosa and into the lymphatic vessels located between the layers of the muscular membrane.

innervation small intestine. Afferent - muscular-intestinal plexus, which is formed by sensitive nerve fibers of the spinal ganglia and their receptor endings. Efferent - in the thickness of the wall, the parasympathetic musculo-intestinal (most developed in the duodenum) and submucosal (Meisner) nerve plexus.

DIGESTION

Parietal digestion, carried out on the glycocalyx of columnar enterocytes, accounts for about 80-90% of the total digestion (the rest is cavitary digestion). Parietal digestion takes place under aseptic conditions and is highly conjugated.

Proteins and polypeptides on the surface of microvilli of columnar enterocytes are digested to amino acids. Being actively absorbed, they enter the intercellular substance of the lamina propria, from where they diffuse into the blood capillaries. Carbohydrates are digested to monosaccharides. Also actively absorbed and enter the blood capillaries of the visceral type. Fats are broken down into fatty acids and glycerides. They are captured by endocytosis. In enterocytes, they endogenize (change the chemical structure in accordance with the body) and resynthesize. Transport of fats is carried out mainly through the lymphatic capillaries.

Digestion includes further enzymatic processing of substances to final products, their preparation for absorption and the absorption process itself. In the intestinal cavity, extracellular cavitary digestion, near the intestinal wall - parietal, on the apical parts of the plasmolemma of enterocytes and their glycocalyx - membrane, in the cytoplasm of enterocytes - intracellular. Absorption is understood as the passage of the products of the final breakdown of food (monomers) through the epithelium, basement membrane, vascular wall and their entry into the blood and lymph.

COLON

Anatomically, the large intestine is divided into the caecum with appendix, ascending, transverse, descending and sigmoid colon and rectum. In the large intestine, electrolytes and water are absorbed, fiber is digested, and feces are formed. The secretion of large amounts of mucus by the goblet cells promotes the evacuation of stool. With the participation of intestinal bacteria in the large intestine, vitamins B12 and K are synthesized.

Development. The epithelium of the colon and pelvic part of the rectum is a derivative of the endoderm. It grows at 6-7 weeks of fetal development. The muscularis mucosa develops at the 4th month of intrauterine development, and the muscularis a little earlier - at the 3rd month.

The structure of the colon wall

Colon. The wall is formed by 4 membranes: 1. mucous, 2. submucosal, 3. muscular and 4. serous. The relief is characterized by the presence of circular folds and intestinal crypts. No villi.

1. Mucous membrane has three layers - 1) epithelium, 2) lamina propria and 3) muscular lamina.

1) Epithelium single layer prismatic. Contains three types of cells: columnar epitheliocytes, goblet, undifferentiated (cambial). Columnar epitheliocytes on the surface of the mucous membrane and in its crypts. Similar to those in the small intestine, but have a thinner striated border. goblet exocrinocytes contained in large quantities in crypts, secrete mucus. At the base of the intestinal crypts are undifferentiated epitheliocytes, due to which the regeneration of columnar epitheliocytes and goblet exocrinocytes occurs.

2) Own plate of the mucous membrane- thin connective tissue layers between the crypts. There are solitary lymphatic nodules.

3) Muscular plate of the mucous membrane better expressed than in the small intestine. The outer layer is longitudinal, muscle cells are located more loosely than in the inner - circular.

2. Submucosal base. Presented by RVST, where there are a lot of fat cells. Vascular and nervous submucosal plexuses are located. Many lymphoid nodules.

3. Muscular membrane. The outer layer is longitudinal, assembled in the form of three ribbons, and between them a small number of bundles of smooth myocytes, and the inner layer is circular. Between them is a loose fibrous connective tissue with vessels and a nervous musculo-intestinal plexus.

4. Serous membrane. Covers different departments differently (completely or on three sides). Forms outgrowths where adipose tissue is located.

Appendix

An outgrowth of the large intestine is considered a rudiment. But it performs a protective function. Characterized by the presence of lymphoid tissue. Has a light. Intensive development of lymphoid tissue and lymphatic nodules is observed at 17-31 weeks of fetal development.

mucous membrane has crypts covered with a single layer of prismatic epithelium with a small amount of goblet cells.

lamina propria mucosa without a sharp border, it passes into the submucosa, where numerous large accumulations of lymphoid tissue are located. AT submucosal located blood vessels and submucosal nerve plexus.

Muscular membrane has outer longitudinal and inner circular layers. The outside of the appendix is ​​covered serous membrane.

Rectum

The shells of the wall are the same: 1. mucous (three layers: 1)2)3)), 2. submucosal, 3. muscular, 4. serous.

1 . mucous membrane. Consists of epithelium, own and muscular plates. one) Epithelium in the upper section it is single-layered, prismatic, in the columnar zone - multi-layered cubic, in the intermediate zone - multi-layered flat non-keratinizing, in the skin - multi-layered flat keratinizing. In the epithelium there are columnar epithelial cells with a striated border, goblet exocrinocytes and endocrine cells. The epithelium of the upper part of the rectum forms crypts.

2) Own record participates in the formation of folds of the rectum. Here are single lymphatic nodules and vessels. Columnar zone - lies a network of thin-walled blood lacunae, blood from them flows into the hemorrhoidal veins. Intermediate zone - a lot of elastic fibers, lymphocytes, tissue basophils. Solitary sebaceous glands. Skin zone - sebaceous glands, hair. Appear sweat glands of the apocrine type.

3) Muscular plate The mucous membrane consists of two layers.

2. Submucosa. The nerve and vascular plexuses are located. Here is the plexus of hemorrhoidal veins. If the wall tone is disturbed, varicose veins appear in these veins.

3. Muscular membrane consists of outer longitudinal and inner circular layers. The outer layer is continuous, and thickenings of the inner form sphincters. Between the layers there is a layer of loose fibrous unformed connective tissue with vessels and nerves.

4. Serous membrane covers the rectum in the upper part, and in the lower parts of the connective tissue membrane.